Integrated circuits have become the technology of choice for performing electronic functions. The downscaling of minimum device geometries has provided for increases in the functional density of electronic devices. The development of nanoelectronic devices has allowed for the continuing increase in functional density of integrated electronic systems beyond the currently perceived limits for conventional electron devices. The term "nanoelectronics" refers to an integrated circuit technology that permits downscaling of minimum circuit geometries to an order of 0.01 microns.
In nanoelectronics, the behavior of electrons in semiconductors can be understood by considering the wave-like properties of electrons. Two important electron quantum phenomena that can be observed are "tunneling", whereby electrons pass through potential energy barriers, and "resonance", whereby steady state tunneling current is substantially reinforced because of the dimensions of quantized regions through which electrons tunnel. Tunneling and resonance are observed when certain quantum states between adjacent regions are aligned.
To date, several different devices, including diodes and transistors, have been disclosed which make use of these quantum effects. For example, Chou, Allee, Pease, and Harris have disclosed such a device in their paper "Lateral Resonant Tunneling Transistors Employing Field-Induced Quantized regions and Barriers," Proceedings of the IEEE, Volume 79, No. 8, August 1991, pp. 1131-1139. As another example, Yang, Kao, and Shih discussed a Stark-Effect Transistor in their paper "New Field Effect Resonant Tunneling Transistor: Observations of oscillatory Transconductance," Appl. Phys. Lett. 55 (26N), 25 Dec. 1989, pp. 2742-2744.
Although advances have been made in the development of quantum effect devices, a significant area in which progress has been slow is that of digital electronics. Devices which may have applications in digital circuits have been disclosed, but have significant limitations. For example, devices such as those disclosed by Chou, et al. display certain characteristics of semiconductor switching devices. Through use of electric fields, quantized regions can be created between depletion-region-potential-barriers, and resonant tunneling can be observed. Thus, electric current can be switched on or off, depending upon the strength of the electric fields. The performance of such devices, however, is highly dependent upon precise dopant concentrations, and they must be operated only at low temperatures. Devices such as those disclosed by Yang, et al. make use of physical, horizontal potential barriers. In such devices, current flow is effected through use of electric fields generated between front and back gates.
None of the prior art devices provide for quantized regions disposed between non-horizontal physical tunneling barriers, such that quantum states can be separately--and thus digitally--modulated to allow electron tunneling. Thus, a need has arisen for a device that makes use of non-horizontal physical tunneling barriers, such that quantum states of quantized regions existing between the non-horizontal physical tunneling barriers may be modulated by electric fields to allow for current switching. Further, conventional lateral resonant tunneling transistors do not operate at room temperature.